1. Field of the Invention
The invention relates to a method and an apparatus to detect the position of film in a photographic device, such as a camera or the like. The method and device sense position detection holes in the film.
2. Description of Related Art
Japanese Unexamined Patent Application, Sho 57-74735 discloses a device to detect a film's position. This device uses signal detection holes formed on a film, which are distinct and different from holes used for feeding the film. The device detects the passing of the signal detection holes as the film is fed using an optical sensor or electrical switch facing the film supply passage in the camera.
Japanese Unexamined Patent Application Sho 57-202524 discloses a device to determine the position of each picture frame in a film. The device includes detection pins, which can be inserted into holes in the film, to determine the position of the film. When the detection pins are inserted into the holes, the device detects the feeding of a frame of film, by actuating a switch that is in interlocking cooperation with the pin.
Several problems exist in each of the above apparatuses. In Japanese Unexamined Patent Application Sho 57-74735, the signals from the sensor or switch are inverted several times as the film is fed. Therefore, it is necessary to provide the device with a circuit that can generate a signal corresponding to a starting or ending edge of the film that is different from the signal for a picture frame. The structure of the detection circuit becomes complicated with this type of signal generation.
In Japanese Unexamined Patent Application Sho 57-202524, the output signal is inverted when the film supply signal quantity equals the picture frame signal quantity. The relationship between the signals from the switches and for the film position is clear and the structure of the detection circuit is relatively simple. However, problems arise when additional through holes are provided for other purposes. These through holes may detect the recording start position data for the film and be positioned between the position determining holes. Therefore, it is necessary to take precautions not to have additional holes detected by the picture frame detection switch. This leads to a complicated circuit and associated detection device.